Flat noncommutator vibration motor

ABSTRACT

Disclosed is an improved flat vibration motor to be disposed in a mobile communication terminal, etc. for generating a vibration signal. A brushless-type vibration motor without brushes and a commutator is adopted, instead of a brush-type vibration motor with the brushes and commutator. An eccentric portion is disposed on one side of the peripheral surface of a rotor made of a permanent magnet, and one or more pairs of hall sensors are mounted in the vibration motor so as to start and drive the vibration motor. A motor controller may be used as internally or externally disposed on the vibration motor. The arrangement of a stator coil is improved so as to reduce the loss of magnetic flux as well as remove the non-operation points, thereby preventing the starting and driving disorders of the vibration motor, and improving its performance and efficiency.

TECHNICAL FIELD

The present invention relates to an improved flat vibration motor to bedisposed in a mobile communication terminal, etc., for generating avibration signal, and more particularly to a flat brushless-typevibration motor without brushes and a commutator, which is adoptedinstead of a brush-type vibration motor with the brushes and commutator,and includes eccentric means disposed on one side of the peripheralsurface of a rotor made of a permanent magnet; one or more pairs of hallsensors mounted in the vibration motor so as to start and drive thevibration motor; a motor controller internally or externally disposed onthe vibration motor; and a stator coil improved in arrangement so as toreduce the loss of magnetic flux as well as remove the non-operationpoints, thereby preventing the starting and driving disorders of thevibration motor, and improving its performance and efficiency.

BACKGROUND ART

Generally, a vibration motor is employed inside a mobile communicationterminal such as a cellular phone to notify a user of an incoming call.A coin-shaped flat vibration motor, greatly reduced in size andthickness, is widely used to meet the requirements of smaller size,lighter weight and lower power consumption in the mobile communicationterminal.

The flat vibration motor comprises mainly a permanent magnet as a fixedmember and a rotor as a rotation member, and an electric connectionbetween the power supply (+, −) and the rotor is made generally bybrushes and a commutator.

In the early days, vibration was attained using an eccentric platemounted on the output axis of the rotation motor, or a fan-shaped rotormade eccentric as a whole toward its one side and having three armaturecoils mounted thereon with no overlapped portion therebetween.

Such a fan-shaped vibration motor using the fan-shaped rotor includes aneccentric rotor having a plurality of armature coils spatially biasedtoward one side, an axial rod mounted in the center of the eccentricrotor, and an axial bearing and a case, both for supporting theeccentric rotor so that it is freely rotated with the help of the axialrod and the bearing. The fan-shaped vibration motor also includes ahousing made of a bracket, a donut-shaped permanent magnet mounted onthe bracket for providing magnetic flux to the eccentric rotor, brushesdisposed inside the permanent magnet, a brush base inserted therein, anda commutator disposed on one surface of the eccentric rotor so as to bein sliding contact with the top of the brushes.

The vibration motor has such a structure that the eccentric rotor havingthe plurality of armature coils spatially biased toward one side isrotated; the permanent magnet is fixed; and the brush-type motor thatreceives the drive power through the brushes and commutator is adopted,thereby leading to the following problems.

That is, such problems are widely known that, because the vibrationmotor is small in size with a diameter around 10 mm, the brushes andcommutator are weak in their structure and low in durability, in result,shortening the life span; the cost is increased due to difficulty inmanufacturing the brushes and commutator; and spark and noise caused bythe connection structure exerts a bad influence upon the operation ofother various electronic devices.

Because other conventional vibration motors used in the mobilecommunication terminal, etc., also use brush-type motors each having aneccentric unbalancing weight without exceptions, they have the sameproblems. Only a noise filter, etc., is currently available to resolvethese problems.

In addition, since the conventional vibration motors have large air gapsbetween the rotor coils that cause a relatively large amount of magneticflux leakage, there are problems that the vibration motor is lowered inefficiency, and increased in power consumption, consequently reducingthe lifetime of the mobile communication terminals.

DISCLOSURE OF THE INVENTION

Therefore, the present invention has been made in view of the aboveproblems, and it is an object of the present invention to provide a flatbrushless-type vibration motor without brushes and a commutator, insteadof a brushless-type vibration motor currently being used for a mobilecommunication terminal.

It is another object of the present invention to provide a vibrationmotor wherein one or more pairs of hall sensors for detecting (sensing)magnetic poles and their positions of a permanent magnet rotor aredisposed in a receiving space that is secured in an internal side of astator of the vibration motor to which two or three field coils arefixed, so as to enable the starting and driving of the vibration motor,and a controller of the vibration motor is mounted in one of twoavailable mounting positions, one in the receiving space, and the otherexternally.

It is a further object of the present invention to provide a vibrationmotor wherein the hall sensors are integrated as one body with anintegrated circuit (IC) element for controlling the vibration motor soas to simplify the entire circuit and reduce the manufacturing cost.

It is yet another object of the present invention to provide a vibrationmotor wherein the stator field coils are improved in arrangement forreducing the loss of magnetic field; and the field coils are disposed tobe overlapped with each other, or the boundary between the field coilsis not coincident with the virtual line outwardly extending from thecenterline of the axial rod in a radial direction, so as to remove thenon-operation points, consequently preventing operating disorders andfurther improving its efficiency and performance.

In accordance with the present invention, the above and other objectscan be accomplished by the provision of a noncommutator vibration motorcomprising: upper and lower cases made of ductile magnetic material; arotor made of a permanent magnet having two or more magnetic poles or adonut-shaped permanent; a ductile magnetic body bonded to the rearsurface of the permanent magnet; stator field coils for generating arotating magnetic field to rotate the permanent magnet; an axial rod onwhich the permanent magnet is axially mounted with a bearing; aninsulating stator to which the axial rod and the field coils are fixed;one or more pairs of hall sensors for detecting the magnetic poles andtheir positions of the permanent magnet; a motor controller forcontrolling an overall operation of the vibration motor; and eccentricmeans fixed to one side of the peripheral surface of the permanentmagnet.

Preferably, the insulating stator is defined at its one internal sidewith a receiving space to dispose therein one or more pairs of left andright hall sensors, the motor controller connected to the hall sensors,or the hall sensors integrated as one body with an integrated circuitelement for controlling the motor, so that the hall sensors disposed inthe receiving space can detect (sense) and control the magnetic poles(or their variations) and their positions of the rotor permanent magnet.

Preferably, the boundary between the field coils may not be coincidentwith or parallel to the virtual line outwardly extending from the centerof the axial rod in a radial direction. Alternatively, field coilsneighboring each other are overlapped in arrangement, so as to removethe non-operation points.

Preferably, the permanent magnet may be mounted eccentrically to theaxial rod, instead of using eccentric means bonded to one side of theperipheral surface of the permanent magnet.

Preferably, the vibration motor controller may includes: the hallsensors; OP amps for comparing and outputting signals inputted from thehall sensors; a control unit for controlling the starting and driving ofthe motor; a plurality of motor drivers; and the field coils connectedto the motor drivers, respectively.

Preferably, the control unit may include: a waveform shaping circuit forshaping the waveform of the signals inputted from the hall sensors; alogic circuit for determining the sequence of powers supplied to thefield coils based on the shaped signal; a duty setting circuit fordetermining the output duty and the power-feed timing signal from thelogic circuit; and switching means for determining and changing thepower-feed direction with respect to the field coils, based on theoutput duty signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is an outline perspective view showing a vibration motor of apreferred embodiment according to the present invention;

FIGS. 2 and 3 are sectional and plane views of FIG. 1;

FIGS. 4 to 7 are plane views showing a vibration motor according toanother embodiment of the present invention;

FIG. 8 is a vertical sectional view showing the vibration motoraccording to another embodiment of the present invention;

FIG. 9 is a plane view showing a permanent magnet (rotor) on whicheccentric means is mounted;

FIG. 10 is a block diagram showing a control circuit of a vibrationmotor controller according to the present invention;

FIG. 11 is a plane view showing a vibration motor employing two fieldcoils according to another embodiment of the present invention;

FIG. 12 is a sectional view of FIG. 11;

FIG. 13 is a block diagram showing a control circuit of the vibrationmotor shown in Fig. 11;

FIG. 14 is a timing chart regarding the control circuit of FIG. 13; and

FIG. 15 is a sectional view showing an alternative arrangement to theembodiment of FIG. 2.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 and 2 are perspective-outline and sectional views, respectively,showing the main part of a flat brushless-type vibration motor 2 withoutbrushes and a commutator, according to the present invention.

The vibrator motor 2 according to the present invention includes upperand lower cases 4 and 6 made of ductile magnetic material, a permanentmagnet 8 as a rotor, a ductile magnetic body 10 bonded to the rearsurface of the permanent magnet 8, and stator field coils C1, C2, and C3for generating a rotating magnetic field so as to rotate the permanentmagnet 8. An axial bearing 12 is fitted in the center hole of theductile magnetic body 10. An axial rod is coupled to the center hole ofthe axial bearing 12. The axial rod 14 and the field coils C1, C2, andC3 are fixed to an insulating stator 16. The vibration motor 2 alsoincludes one or more pairs of hall sensors (in the illustratedembodiment, H1 and H2) for detecting magnetic poles and their positionsof the permanent magnet 8, a motor controller 18 for controlling theoverall operation of the vibration motor 2, and a power-feed terminal 20for transferring drive power and an external control signal to thevibration motor 2 and the motor controller 18, respectively. A receivingspace 22 is defined for disposing therein the hall sensors H1 and H2alone, or together with the motor controller 18. Eccentric means 24 isfixed to the peripheral surface of the permanent magnet 8.

In the present invention, the cases 4 and 6 and the ductile magneticbody are all made of a magnetic material that shows a property ofmagnetization by a magnet's approach and demagnetization by its removal.The cases 4 and 6 serve as a protector of their internal parts as wellas a magnetic shield. A reference numeral 26 denotes a washer.

The permanent magnet 8 with two or more alternately-arranged magneticpoles (N or S) is mounted in such a manner that it faces the stator 16.Its rotation direction is determined based on the sequence of magneticfields generated from the field coils C1, C2, and C3 by the motorcontroller 18.

The ductile magnetic body 10 prevents the magnetic field of thepermanent magnet 8 from escaping backward as well as from beingdisturbed.

In addition, the hall sensors H1 and H2 are disposed in the receivingspace 22 alone, combined with the motor controller 18 as shown in FIG.3, or integrated into a one-chip IC element for controlling thevibration motor as shown in FIG. 5. The hall sensors H1 and H2, whichare disposed to face the permanent magnet 8, detect the positions orvariations of magnetic poles, and then the detected result is inputtedto the motor controller 18.

That is, the hall sensors detect the rotor's position and input thedetected signals to the motor controller 18.

The motor controller 18 determines the sequence of powers supplied tothe field coils C1, C2, and C3 during the operation of the vibrationmotor 2, based on the input signal mentioned above, for starting anddriving the vibrating motor 2. The motor controller 18 is positionedinternally in the vibration motor 2 as shown in FIGS. 3 and 5 in whichit is disposed in the receiving space 22 together with the hall sensorsH1 and H2. The motor controller may also be externally disposed on thevibration as shown in FIG. 4 in which it is electrically connected tothe hall sensors H1 and H2.

As described above, the rotor includes the axial rod 14, the axialbearing 12, the permanent magnet 8, and eccentric means (unbalancingweight) 24 fixed or attached to one side of the peripheral surface ofthe permanent magnet 18. The axial bearing 12 is generally made of ametal bearing.

The field coils C1, C2, and C3 are made of fine-diameter conductingwires, such as enamel wires, wound to have a desired structure. Coresmay be employed, and their omission is also permitted. But, it ispreferable that at least two cores, or preferably three, are mounted onthe stator 16 at positions corresponding to the permanent magnet 8positioned above the cores.

The field coils C1, C2, and C3 and the axial rod 14 are molded into theinsulating stator 16 by insertion molding, and the field coils C1, C2,and C3 are connected at their end portions to the motor controller 18through the terminal 20.

A mounting-coverage angle of the eccentric means 24 of 180° or more,fixedly disposed along the peripheral surface of the permanent magnet,causes a decrease in the vibration force, and, on the other hand,mounting-coverage angle of less than 20° to 30° causes a decrease in theefficiency of the vibration motor, resulting in its overload. Therefore,according to the present invention, it is preferable that themounting-coverage angle is determined in the range between an angle muchhigher than 20° to 30° and an angle much less than 180°, that is, around100°. In addition, the amount of magnetic field sufficient for thesmooth rotation of the vibration motor 8 is obtained when the sum ofmounting-coverage angles of the field coils C1, C2, and C3 is set tomore than 150°.

The unbalancing body as the eccentric means 24 is generally made of aweighty material with high specific gravity. Since the unbalancing bodyis fixedly attached to the peripheral surface of the rotor, thepermanent magnet 8, it is also made of non-magnetic metal or non-metalweighty material so as to exert no influence upon the magnetic field ofthe permanent magnet 8.

The reason why the eccentric means 24 is made of weighty material is toobtain the amount of eccentricity sufficient for causing the vibration,but the vibration may also be obtained by disposing the permanent magnet8 eccentrically to the axial rod 14 without the unbalancing weight, asshown in FIG. 15.

When the vibration motor 2 is configured such that the rotor permanentmagnet 8 is disposed eccentrically to the axial rod according to thepresent invention, the vibration motor can be manufactured in smallsize, removing separate eccentric means (unbalancing weight) to complywith the current smaller-size trend.

In addition, because the eccentric means 24 can be fixed to any positionof the peripheral surface of the permanent magnet 8, it has an advantagein that there is no need to set the fixed position, making itsmanufacture easier.

In the stator 16 of the present invention, the biased arrangement of thefield coils C1, C2, and C3 allows the receiving space 22 to be formed atone side thereof for disposing therein one or more pairs of hall sensorsH1 and H2, or the motor controller 18 combined with the hall sensors H1and H2.

As shown in FIG. 3, when the boundaries between the field coils C1, C2,and C3 are coincident with or parallel to the virtual line O outwardlyextending from the center of the axial rod 14 in a radial direction,non-operation points may be generated. Therefore, in the presentinvention, the field coils C1, C2, and C3 are disposed in the stator 16in such a shape that the boundaries are not coincident with or parallelto the virtual line O as shown in FIGS. 6 and 7, so as to remove thenon-operation points and prevent the operation disorder of the vibrationmotor 8.

In addition, the field coils C1, C2, and C3 are disposed in such amanner that the field coils C1 and C2 are vertically overlapped as shownin FIG. 8, and also the field coils C2 and C3 are also verticallyoverlapped, so that there is no in-plane boundary portion, therebypreventing operating disorders of the vibration motor 8, as well asimproving its efficiency.

FIG. 10 is a circuit diagram showing the controller 18 of the vibrationmotor, according to one embodiment of the present invention. Thecontroller 18 includes the hall sensors H1 and H2, OP amps OP1 to OP4for comparing and outputting signals from the hall sensors H1 and H2,and a control unit for controlling the starting and driving of thevibration motor 2 a based on signals from the OP amps OP1 to OP4. Thecontroller 18 also includes a plurality of motor drivers D1, D2, and D3for amplifying the output from the control unit, and the field coils C1,C2, and C3 connected to the outputs of the motor drivers D1, D2, and D3,respectively.

The control unit includes therein a waveform shaping circuit(Schmitt-trigger circuit) for shaping the form of the signals from thehall sensors H1 and H2, and a logic circuit for determining the sequenceof powers supplied to the field coils C1, C2, and C3, based on theshaped signal. The control unit also includes a duty setting circuit forsetting the output duty and the power-feed timing signal from the logiccircuit, and a switching circuit for determining and shifting thepower-feed direction based on the output duty signal.

The following table shows the signal outputs from the hall sensors H1and H2, for example, according to the magnetic poles or their positionsof the permanent magnet 8 when it has six magnetic poles.

TABLE 1 (Example of signals from the hall sensors that detect thepolarities of the permanent magnet with 6 magnetic poles) Address 1 2 34 5 6 H1 0 H H H H 1 H H H H H2 2 H H H 3 H H H Output C1 C3 C1 C2 C3 C2

Now, a description will be given of the starting and driving states ofthe vibration motor 2 using the example of Table 1.

When signal ‘H’ (active) is provided to both the address 1 of the hallsensor H1 and the address 2 of the hall sensor H2 according to theposition of the permanent magnet 8, power supply voltage is fed to thefield coil C1, starting and driving the vibration motor 2. When signal‘H’ is provided to the addresses 0 and 1 of the hall sensor H1 and theaddress 2 of the hall sensor H2, power supply voltage is fed to thefield coil C2, starting and driving the vibration motor 2.

Of course, the present invention is not limited to the above-mentionedexample, and the output state may be varied according to the number ofmagnetic poles of the permanent magnet 8 or its program.

On the other hand, FIGS. 11 and 12 are schematic plane and sectionalviews showing the vibration motor 2 a according to another embodiment ofthe present invention wherein the field coils C4 and C5 are positionedat both sides of the insulating stator 16. Its most parts are similar tothose of the vibration motor 2 that employs three field coils C1, C2,and C3, but the field coils C4 and C5 are differently positioned inarrangement because the number of field coils C4 and C5 is two.Therefore, there are differences also in the circuit for supplying thecontrol power to the two field coils C4 and C5 as well as in the controltimings for rotating smoothly the rotor (permanent magnet).

That is, the vibration motor 2 a includes upper and lower cases 4 and 6,the rotor permanent magnet 8, the ductile magnetic body 10 attached tothe rear surface of the rotor permanent magnet 8, and the stator fieldcoils C4 and C5 for generating the rotating magnetic field to rotate thepermanent magnet 8. An axial bearing 12 is coupled to the center axialhole of the ductile magnetic body 10. An axial rod 14 is coupled to thecenter hole of the axial bearing 12. The axial rod 14 and the fieldcoils C4 and C5 are fixed to an insulating stator 16. The vibrationmotor 2 a also includes one or more pairs of hall sensors H1 and H2 fordetecting the magnetic poles and their positions of the permanent magnet8, a motor controller 18 a for controlling the overall operation of thevibration motor 2, and a power-feed terminal 20 for transferring thedrive power and the external control signal to the vibration motor 2 andthe motor controller 18 a, respectively. A receiving space 22 is definedfor disposing therein the hall sensors H1 and H2 alone, or together withthe motor controller 18 a. Eccentric means 24 is fixed to the peripheralsurface of the permanent magnet 8.

The field coils C4 and C5 may be radially disposed, respectively, inboth left and right sides of the insulating stator 16 for the smoothoperation of the vibration motor 2 a. However, because the receivingspace 22 is positioned at one internal side of the insulating stator 16,both the field coils are positioned so as not to be directly opposite toeach other, as shown in FIG. 11, being aside from the receiving space22.

The field coils C4 and C5 are disposed symmetrically with respect to thevertical centerline. It is preferable that the mounting-coverage angleθ1 of the field coil C4 is around 90° and the angle θ2 between thevertical centerline and the field coil C4 is around 15° so as not tonegatively influence the starting and driving of the vibration motor 2 awhile securing the space margin for the receiving space 22 and the hallsensors H1 and H2.

The permanent magnet 8 with two or more alternately-arranged magneticpoles N and S is disposed so as to face the stator 8. The starting andthe driving direction (rotation direction) are determined based on thesequence of magnetic fields generated from the field coils C4 and C5 bythe motor controller 18 a.

In addition, one or more pairs of hall sensors H1 and H2 are disposed,facing the permanent magnet 8, in the receiving space 22 alone orcombined with the motor controller 18 a, or unified or integrated as onechip with an IC element for controlling the vibration motor 2 a. Thehall sensors H1 and H2 detect the variations or positions (or rotor'sposition) in the magnetic poles of the permanent magnet 8 and then inputthem to the motor controller 18 a.

FIG. 13 is a block diagram showing a control circuit of the vibrationmotor 2 a according to another embodiment of the present invention. Thisis mostly similar to the circuit shown in FIG. 10. But, since the numberof field coils C4 and C5 connected to the output of the control unit istwo and the field coils C4 and C5 alternately generate the magneticpoles N and S, the number of drivers D4 and D5 having the function ofchanging the polarity (+, −) of power source voltage is set to two, andthe field coils C4 and C5 are connected to the outputs of the driver D4and D5, respectively.

The motor controller 18 a determines the shift-timing of the voltagepolarity (+) (−) applied to the field coils C4 and C5 during thestarting and driving of the vibration motor 2 a, based on the positionof the rotor inputted from the hall sensors H1 and H2, so as to startand drive the vibrating motor 2. The motor controller 18 a may bepositioned internally in the vibration motor 2, as mentioned above, inwhich it is disposed in the receiving space 22 together with the hallsensors H1 and H2. The motor controller 18 a may also be externallydisposed on the vibration motor 2, in which it is electrically connectedto the hall sensors H1 and H2.

In addition, the control unit includes therein a waveform shapingcircuit for shaping the form of signals from the hall sensors H1 and H2,and a switching circuit and a logic circuit for determining and changingthe shift-timing of the voltage polarity (+) (−) and the sequence ofpowers supplied to the field coils C4 and C5 based on the shaped signal.

In the driver D4, the polarity (+) (−) of power supply voltage appliedto the field coil C4, as well as the magnetic field of the field coilC4, is changed according to the output state of the terminals D and Econnected to the outputs of the control unit. Also, in the driver D5,the polarity (+) (−) of power supply voltage applied to the field coilC5, as well as the magnetic field of the field coil C4, is changedaccording to the output state of the terminals F and G connected to theoutputs of the control unit.

For example, when signal ‘H’ (active) is outputted from the outputterminal D of the control unit, and signal ‘L’ is outputted from theoutput terminal E thereof, the voltage of polarity (+) is outputted fromthe output terminal Da of the driver D4, and the voltage of polarity (−)is outputted from the output terminal Ea of the driver D4. During thisperiod, an S-pole magnetic field is generated from the field coil C4.

On the contrary, when signal ‘L’ is outputted from the output terminal Dof the control unit, and signal ‘H’ is outputted from the outputterminal E thereof, the voltage of polarity (−) is outputted from theoutput terminal Da of the driver D4, and the voltage of polarity (+) isoutputted from the output terminal Ea of the driver D4. During thisperiod, an N-pole magnetic field is generated from the field coil C4.

In addition, when signal ‘H’ (active) is outputted from the outputterminal F of the control unit, signal ‘L’ is outputted from the outputterminal G thereof, the voltage of polarity (+) is outputted from theoutput terminal Fa of the driver D5, and the voltage of polarity (−) isoutputted from the output terminal Ga of the driver D5. During thisperiod, S-pole magnetic field is generated from the field coil C5.

On the contrary, when signal ‘L’ is outputted from the output terminal Fof the control unit, and signal ‘H’ is outputted from the outputterminal G of thereof, the voltage of polarity (−) is outputted from theoutput terminal Fa of the driver D5, and the voltage of polarity (+) isoutputted from the output terminal Ga of the driver D5. During thisperiod, an N-pole magnetic field is generated from the field coil C5.

FIG. 14 is a timing chart illustrating the starting and driving of thevibration motor 2 a according to said another embodiment of the presentinvention.

That is, when the initial position signal of the rotor inputted to thehole sensor H1 is N (N1), power supply voltage is fed to the field coilC4 by the controller 18 a to generate S-pole magnetic field, causingmagnetic attraction that allows rotation of the rotor toward the fieldcoil C4. With the rotor being rotated about 60°, power supply voltage isfed to the field coil C5 to generate an N-pole magnetic field, causing amagnetic force to attract the magnetic pole S1 of the rotor. In suchoperation, a phase difference of 30° between the field coils C4 and C5causes continued change in the magnetic field, allowing driving of thevibration motor 2 a and its eccentric rotation.

In this another embodiment, the number of field coils C4 and C5 is two,so that the stator and the control circuit may be formed in simplemanner, and also the manufacturing cost and the weight may be reduced.

In the present invention, a hall sensor, one of magnetic-sensitiveelements, is used, as an example, for detecting the magnetic poles N andS of the permanent magnet 8. However, other magnetic-sensitive elementsmay also be used, such as a lead switch, a read switch, a magneticresistance element, a thermo-magnetic sensitive element, a magneticdiode, a magnetic transistor, and a magnetic thyrister. The otheravailable elements are a photo sensor, an image sensor, a proximitysensor, etc.

When using the photo sensor, the image sensor, or the proximity sensor,a plurality of reflectors may be formed in a predetermined arrangementon a surface of the permanent magnet at position corresponding to thesensors. Alternatively, an image reflector may be formed thereon in anarrangement according to differences in reflection or chromaticity, ordetect-target means of the proximity sensor may be formed thereon.

INDUSTRIAL APPLICABILITY

The present invention adopts a brushless-type vibration motor withoutbrushes and a commutator, instead of a brush-type vibration motor withbrushes and a commutator. This makes the manufacturing process easier,and prevents problems experienced in the conventional vibration motorsuch as poor durability, short life span, and generation of spark andnoise due to the connection structure, each caused by the small-sizebrushes and commutator.

In addition, the non-operation points are removed, preventing operatingdisorders, and the boundary between the field coils is narrowed or thein-plane boundary portion is removed to further reduce the leakageamount of magnetic field, thus attaining lower power consumption of thevibration motor, and improving the efficiency. This results in longerlifetime of the mobile communication terminal.

Further, in another embodiment that employs two field coils, the statorand the control circuit are simplified in structure to allow reductionin the manufacturing cost and the weight.

Furthermore, the motor controller can be mounted in the internalreceiving space in the vibration motor, so that the space utilizationbecomes excellent, and also the hall sensors and the IC element forcontrolling the motor are made as one chip, thereby reducing themanufacturing cost and improving the reliability of operation.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A flat brushless-typo vibration motor comprising: a rotor made of anaxially-mounted permanent magnet with two or more magnetic poles; aductile magnetic body bonded to a rear surface of the permanent magnet;three stator field coils arranged asymmetrically in a circumferentialdirection for generating a rotating magnetic field to rotate thepermanent magnet; an insulating stator to which an axial rod and thefield coils are fixed and defining a receiving space; one or more pairsof hall sensors for detecting the magnetic poles and their positions ofthe permanent magnet, said hall sensors disposed in said receivingspace; a motor controller disposed in said receiving space forcontrolling an overall operation of the vibration motor; and eccentricmeans fixed to one side of a peripheral surface of the permanent magnet.2. The flat brushless-type vibration motor according to claim 1, whereinthe hall sensors are mounted on and electrically connected to the motorcontroller.
 3. The flat brushless-type vibration motor according toclaim 1, wherein the hall sensors are integrated with the motorcontroller in the form of a one-chip IC element.
 4. The flatbrushless-type vibration motor according to claim 1, wherein at leastone boundary line between the field coils is not coincident with orparallel to a virtual line outwardly extending from a center of theaxial rod in a radial direction, whereby there is no non-operationpoint.
 5. The flat brushless-type vibration motor according to claim 1,wherein the field coils neighboring each other are disposed to beoverlapped with each other in a circumferential direction, whereby thereis no non-operation point.
 6. The flat brushless-type vibration motoraccording to claim 1, wherein the motor controller comprises: the hallsensors for detecting the position of the permanent magnet; OP amps forcomparing and outputting signals inputted from the hall sensors; acontrol unit for controlling starting and driving of the vibration motorwith reference to signal inputted from the OP amps; a plurality of motordrivers for amplifying signals outputted from the control unit; and thefield coils connected to the drivers, respectively.
 7. A flatbrushless-type vibration motor comprising: a motor made of anaxially-mounted permanent magnet with two or more magnetic poles; aductile magnetic body bonded to a rear surface of the permanent magnet;two stator field toils arranged asymmetrically in a circumferentialdirection for generating a rotating magnetic field to rotate thepermanent magnet; an insulating stator to which an axial rod and thefield coils are fixed and defining a receiving space; one or more pairsof hall sensors for detecting the magnetic poles and their positions ofthe permanent magnet, said hall sensors disposed in said receivingspace; a motor controller disposed in said receiving space forcontrolling an overall operation of the vibration motor; and eccentricmeans fixed to one side of a peripheral surface of the permanent magnet.8. The flat brushless-type vibration motor according to claim 7, whereinthe motor controller includes: the hall sensors for detecting theposition of the permanent magnet; OP amps for comparing and outputtingsignals inputted from the hall sensors; a control unit for controllingstarting and driving of the vibration motor with reference to signalsinputted from the OP amps; a plurality of drivers for shifting polarity(+) (−) of power supply voltage provided to the field coils according tosignals outputted from the control unit; and the field coils connectedto the drivers, respectively.
 9. The flat brushless-type vibration motoraccording to claim 7, wherein the field coils are disposed,respectively, at both internal side of the insulating statorsymmetrically with respect to a vertical centerline of the insulatingstator; the mounting-coverage angle of one of the field coils is around90°; and angle between the vertical centerline and one of the fieldcoils is around 15°.
 10. A flat brushless-type vibration motorcomprising: a rotor made of an axially-mounted permanent magnet with twoor more magnetic poles; a ductile magnetic body bonded to a rear surfaceof the permanent magnet; three stator field coils arrangedasymmetrically in a circumferential direction for generating a rotatingmagnetic field to rotate the permanent magnet; an insulating stator towhich an axial rod and the field coils are fixed and defining areceiving space; one or more pairs of ball sensors for detecting themagnetic poles and their positions of the permanent magnet, said halldispensers disposed in said receiving space; and a motor controllerdisposed in said receiving space for controlling an overall operation ofthe vibration motor, wherein the rotor permanent magnet is disposedeccentrically to the axial rod so as to cause its vibration.